CA-134745: read device-type and mode on physical-device callback

This is how blkback does it.

Signed-off-by: Thanos Makatos <thanos.makatos@citrix.com>
Acked-by: Chandrika Srinivasan <chandrika.srinivasan@citrix.com>
CA-134745: don't write info on physical-device callback

This write appears redundant as we already do so when connecting to the
front-end (connect_frontend), just like blktap does.

Signed-off-by: Thanos Makatos <thanos.makatos@citrix.com>
Acked-by: Chandrika Srinivasan <chandrika.srinivasan@citrix.com>
CA-134745: simplify and clarify reconnect logic

Signed-off-by: Thanos Makatos <thanos.makatos@citrix.com>
Acked-by: Chandrika Srinivasan <chandrika.srinivasan@citrix.com>
CA-134745: ensure frontend() is called before physdev/hotplug.

Functions physical_device_changed() and hotplug_status_changed() require the
front-end path in the VBD to have been initialised, this patch ensures
that frontend() has been called before any of these functions are
called.

Signed-off-by: Thanos Makatos <thanos.makatos@citrix.com>
Acked-by: Chandrika Srinivasan <chandrika.srinivasan@citrix.com>
Merge branch 'CA-134745' into xs64bit

Signed-off-by: Thanos Makatos <thanos.makatos@citrix.com>

GitHub: closes #85 on xapi-project/blktap